Re: memory usage issue for double-float operations

(declaim (type (simple-array double-float (5000)) *ar*))

On 25.09.2024 21:44, Matt Kaufmann wrote:
> Hi,
>
> Is there a way to modify the example below so that the final form does
> not allocate memory in SBCL?  (To be fair, I tried several other Lisps
> as well, and all of them allocated memory.)
>
> (declaim (optimize (compilation-speed 0) (debug 0) (speed 3) (space 0)
>                     (safety 0)))
>
> (defvar *ar* (make-array '(5000)
>                           :element-type 'double-float
>                           :initial-element 0.0d0))
>
> (loop with i of-type (integer 0 *) = 0 do
>        (cond ((>= i 5000)
>               (return))
>              (t (progn (setf (aref *ar* i)
>                              (float i 0.0d0))
>                        (setq i (1+ i))))))
>
> (defun foo ()
>    (loop with i of-type fixnum = 0 do
>          (cond
>           ((>= i 4999) ; <-- for i from 0 to 4999 ...
>            (return))
>           (t (setf (aref *ar* i)
>                    (the double-float
>                         (+ 1.0d0
>                            (the double-float (aref *ar* i)))))
>              (setq i (the fixnum (1+ i)))))))
>
> (time (foo))
>
> Thanks,
> Matt
>
>
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